Xeristat

ABSTRACT

This invention relates to a xeristat, which is defined as a device which is sensitive to changes in vapor pressure (i.e., relative humidity) and which gives an electrical signal when the relative humidity passes through some preselected point.

United States Patent lnventor Ralph L. Fenner Mill Valley, Calif. 834,088

June 17, 1969 Jan. 12, 1971 Hy rometrix, Inc.

App]. No. Filed Patented Assignee [56] References Cited UNITED STATES PATENTS 2,267,164 12/1941 Newton 337/300 3,135,117 6/1964 Fenner.... 73/337 3,198,011 8/1965 Fenner 73/3375 Primary ExaminerRobert K. Schaefer Assistant Examiner-M. Ginsburg Att0rney-Robyn Wilcox ABSTRACT: This invention relates to a xeristat, which is defined as a device which is sensitive to changes in vapor pressure (i.e., relative humidity) and which gives an electrical signal when the relative humidity passes through some preselected point.

PATENTED m 1 2 m INVENTOR.

ATTORNEY The xeristat of the present invention comprises a partially bridled xeric element, such as the one described in nouns in with FIGS. 6 to 8, inclusive, of my copending application e H. tled Xeric Element and Method of Freparirig the Same," filed on June 17, 1969, Ser. No. 834,087. This xeric element is associated with a switch in an electrical circuit, and in its sirnplest (and, therefore, its most preferable) form, is one contact of a bar switch. The xeric element briefly comprises a resilient mctai saddle, preferably beryllium copper, of a thickness of about one one-thousandths of an inch and preferably 14 millimeters in length and 2 millimeters in width. The two ends of the strip are bent back upon a common ace form pockets at each end which have a length of 2 millimeters, leaving the overall length of the element, or xeric chip, at millimeters. The moisture-sensitive element is the rib, or spine, of the seed-throwing arm which forms an extension of the seed pod of a seed-throwing plant, such as Geranium llichardsonii, Geranium caespitosum, Geranium eriostemon, Geranium dissecturn, or the like. After the seeds have matured and have been thrown, the seed pods are harvested, the throwing arms are felted for a period sufficient to loosen the soft fibrous material which covers a major portion of the rib of the throwing arm, and the fibrous material is pulled away as by passing the throwing arm through the fleshy part of tightly compressed fingers of an operator. As described in my said application, the seed-throwing arm in its natural state (when dry) assumes a flat spiral form extending through an arc of between 450 and 540, depending upon the dryness of the environment. When saturated with water, these ribs are straight and strong; and, when thoroughly dry, form a spiral lying in a substantially single plane extending through an arc of about 540, or one and one-half turns. in my preferred xeric element, I take a length of 10 millimeters of such a rib for use as the moisture-sensitive member and place one or more (preferably three) such elements in the metallic saddle. While the vegetable fibers are still thoroughly saturated, I quickly dip each end of the metal plate in fluid solder in order to fill the ends of the pockets with fluid solder and rigidly secure the ends of the fibers to the respective ends of the metallic plate. At this point the chip is perfectly straight. However, when the vegetable fibers are permitted to dry, their warp force bends the metal plate (as is shown by comparison of FIGS. l and 2 of this application) to form an arc, the ends of which lie at an angle of about 60 with respect to each other. As the elements dry, they exert a constant warp force upon the metal member which causes it to bend in equal increments directly proportional to relative humidity from the 100 percent humidity of the straight form shown in FIGS. 2 and 3. in its simplest form, the xeristat comprises an electrical circuit in which the chip comprises one bar of a single bar switch. it will be obvious to those skilled in the art that the other bar of the switch can be bent so as to cause engagement of the two parts of the switch at any preselected degree of relative humidity.

OBJECTS It is a primary object of the present invention to provide a device which is sensitive to relative humidity, or vapor pressure, and which either makes or breaks an electrical circuit when the environment passes through some reselecte degree of relative humidity.

it is another object of the present invention to provide a device of the class described which is simple in construction, reliable in its operation, and which has a long life.

These and other objects of the invention will be apparent from the following detailed description of the device, taken in conjunction with the accompanying drawings in which:

FIG. 1 is a greatly enlarged perspective View of the chip, or partially bridled xeric element, of the above-mentioned application, showing its form when the moisture-sensitive fibers register saturation, or 100 percent relative humidity.

FIG. 2 is a perspective view of the element of HG. i shown in the form which it assumes when the fibrous moisture-sensitive elements are completely dry.

FIG. 3 is a perspective view of a bar switch in which one bar is the xeric element of FIGS. l and 2, the switch being closed and indicating that the xeric element is registering the dry state.

FIG. 4 is a perspective view of the switch of FIG. 3 shown with the switch open and indicative of the switch in a moist environment.

In the preferred form of my invention, I prefer to use a bridled element of the type shown in FIGS. 6 to 8, inclusive, of my above-mentioned application. Such an element has the xeric element attached to its supporting plate only at its-ends and hence is really only partially bridled thereto, but such elements in this art are commonly referred to as bridled as it is assumed that a fully bridled element (i.e., one in which the xeric element is attached to its plate throughout its entire length) will be so specified. The bridled element preferably comprises a saddle formed of thin resilient material, such as beryllium copper, with a thickness of one one-thousandths of an inch. l have-found that a suitable size for practical application of the invention uses a saddle formed of sheet 25 of such material having a length of 14 millimeters and a width of 2 millimeters. Each end 26 is bent back upon a common face to form a pocket 28 at the respective ends of the chip, each tab 26 having a length of 2 millimeters. This leaves a chip, or saddle, having a pocket 28 at each end, with an overall length of 10 millimeters and an overall width of 2 millimeters. The moisture-sensitive element 10 comprises the rib, or spine, 10 of the throwing arm of the seed pod of a seed-throwing plant, such as one of the four specifically mentioned above. The seed pods are harvested after the seeds have been thrown. Preferably, the throwing arms are removed from the remainder of the seed pod and these arms are soaked in warm water, preferably held to the temperature of the range from about to about F. for a period of about 3 weeks, or until the fibrous covering of a rib of the arm is readily separated from the rib by pulling the arm through tightly compressed fingers of an operator. A section of 9 millimeters in iength is taken from these ribs it) to be used in the bridled element. Since the ribs of the preferred plants are flat on one side and rounded on the other, it is a simple matter to place them flat on the chip 25; and if more than one element is used on a chip to place all of them flat side against the chip so that the warp force of all of them work in the same direction. Preferably, three or four such elements 10 are used as l have found that they equalize the small variances that may be found in individual elements and several are desirable to easily overcome the antibending characteristics of the chip. The desired number of ribs 10 are placed on the chip 25 with their ends placed in the respective pockets 28, and are immediately dip soldered in melted solder to fill the pockets 23 with solder 27, and thus rigidly attach the ends of the respective fibers to the respective ends of the saddle 25. While the members 10 are of vegetable composition and, therefore, can be burned (and do suffer an irreversible loss of effectiveness if heated to a temperature of above C.), the momentary dipping of the completely saturated fibers in the liquid solder does not harm them. The resultant chip, or bridled element, at this stage continues to assume the form show in FIG. 1 in which the saddle .25 is perfectly straight. However, as soon as the fibrous elements are permitted to dry, their warp force (each element exerting a warp force when dry of about five gram-s) cause the saddle 25 to bend to form the arcuate member shown in FIG. 2. Since the elements 10 in their dry and natural state form a helix lying in a single plane, the saddle 25 is subjected to a simple bending action and not to a complicated twisting.

if one end of the bridled element 25 is soldered to one wire 26 of an electric circuit, it can form one contact of a bar switch. The other contact 35 of the bar switch is connected to the other wire as and is so located as to engage the member 25 when that member has bent to a predetermined degree, thus forming a xeristatic switch. it is obvious that the degree of relative humidity at which the switch is open or closed can readily be determined by those skilled in the art. Accordingly, the bar contact 5 is so located from the element 25 that the two engage at the predetermined degree of humidity. in the form shown in FIGS. 3 and 4, the contact 35 can readily be bent to cause closing of the switch at any selected degree of relative humidity. It is obvious that when the environment in which the xeristat is located is saturated, i.e., 100 percent relative humidity, the element 25 will assume the straight position shown in FIG. 4 and that as humidity decreases, the member 25 will bend toward the bar contact 35 and will engage that bar contact when the desired degree of humidity is reached. The relative position of the element 25 and the bar switch determines the point at which the two members engage or disengage, and the degree of relative humidity at which the switch is to make or break. Consequently, the distance which the two contacts should be placed from each other can readily be determined by those skilled in the art. Obviously, the xeristat of the present invention can be used to break the switch when the environment in which the Xeristat is located becomes too dry, or to close the switch when the environment exceeds a preselected degree of humidity.

It is also obvious that the contact can readily be made adjustable, so that the degree of humidity will make or break the switch can be readily adjustable by the user. For example, if the contact 35 is perpendicular to the movement of the chip 25, and in the same plane; and is adjustable (as by being threaded through a suitable nut), it is obvious that the adjustment of the switch is readily made by an operator.

It will be understood that the drawings and the above disclosure show a preferred embodiment of my invention and that many modifications will occur to those skilled in the art which will not depart from the inventive concepts herein disclosed. For example, it is obvious to those skilled in the art that the bridled xeric element does not have to form one contact of a bar switch but can be utilized by suitable linkage to close or open a separate switch. Also, the switch can be made easily adjustable, if desired. Accordingly, it is intended that the ap pended claims cover such modifications as fall within the true spirit and concepts of the invention.

lclaim:

l. A xeristatic switch comprising: a saddle formed of a thin resilient metal, a moisture-sensitive fiber taken from the seedthrowing arm of the seed pod of the group of plants consisting of Geranium dissectum, Geranium Richardsonii, Geranium caespitosum, and Geranium eriostemon, means rigidly securing the fiber at its ends to the ends of the saddle, means connecting one end of the saddle to an electric circuit, a switch contact held in spaced relationship to the said saddle, and means for connecting said switch contact to said electric circurt.

2. The xeristatic switch of claim 1 in which the saddle comprises a sheet of beryllium copper with a thickness of approximately one one-thousandths of an inch.

3. The device of claim l in which the moisture-sensitive fiber is taken from the seed pod of the Geranium dissectum,

4-. The device of claim-1 in which the moisture-sensitive fiber is taken from the seed pod of Geranium Richardsonii.

5. The device of claim 1 in which the moisture-sensitive fiber is taken from seed pod of Geranium caespitosum.

6. The device of claim 1 in which the moisture-sensitive element is taken from the seed pod of Geranium eriostemon.

7. The xeristatic switch of claim 1 in which the seed-throwing arm of the plants mentioned constitutes the rib with a fibrous covering, and the moisture-sensitive fiber constitutes the rib without the covering.

8. A xeristatic switch adapted to be inserted in an electric circuit, comprising: a xeric element comprising a saddle formed of a thin resilient metal, a moisture-sensitive fiber taken from the seed-throwing extension of the seed pod of the group of plants consisting of Geranium dissectum, Geranium Richardsonii, Geranium caespitosum, and Geranium exiastemon, and means securing the moisture-sensitive fiber to the metallic saddle, and means including said xeric element for opening and closing said switch. 

1. A xeristatic switch comprising: a saddle formed of a thin resilient metal, a moistuRe-sensitive fiber taken from the seedthrowing arm of the seed pod of the group of plants consisting of Geranium dissectum, Geranium Richardsonii, Geranium caespitosum, and Geranium eriostemon, means rigidly securing the fiber at its ends to the ends of the saddle, means connecting one end of the saddle to an electric circuit, a switch contact held in spaced relationship to the said saddle, and means for connecting said switch contact to said electric circuit.
 2. The xeristatic switch of claim 1 in which the saddle comprises a sheet of beryllium copper with a thickness of approximately one one-thousandths of an inch.
 3. The device of claim 1 in which the moisture-sensitive fiber is taken from the seed pod of the Geranium dissectum.
 4. The device of claim 1 in which the moisture-sensitive fiber is taken from the seed pod of Geranium Richardsonii.
 5. The device of claim 1 in which the moisture-sensitive fiber is taken from seed pod of Geranium caespitosum.
 6. The device of claim 1 in which the moisture-sensitive element is taken from the seed pod of Geranium eriostemon.
 7. The xeristatic switch of claim 1 in which the seed-throwing arm of the plants mentioned constitutes the rib with a fibrous covering, and the moisture-sensitive fiber constitutes the rib without the covering.
 8. A xeristatic switch adapted to be inserted in an electric circuit, comprising: a xeric element comprising a saddle formed of a thin resilient metal, a moisture-sensitive fiber taken from the seed-throwing extension of the seed pod of the group of plants consisting of Geranium dissectum, Geranium Richardsonii, Geranium caespitosum, and Geranium exiastemon, and means securing the moisture-sensitive fiber to the metallic saddle, and means including said xeric element for opening and closing said switch. 